1. Linggood, F. V., Matthews, A. C., Pinfield, S., Pope, C. G., and Sharland, T. R., Nature, 174, 557 (1954).
2. Linggood, F. V., and Fenton, E. L., Brit. J. Exp. Path., 28, 354 (1947).
3. Chain, E. B., Paladino, S., Callow, D. S., Ugolini, F., and Van Der Sluis, J., Bull. World Health Org., 6, 73 (1952).